An electrical swivel, also termed electrical collector or slip ring joint, is an electro-mechanical device used to transfer electricity between two parts that are mobile relative to each other (one part being considered to be fixed or “geostationary” and the other rotary).
The general principle of such a device relies on the implementation of circular conducting tracks cooperating with mobile brush assemblies in order to establish electrical connections, typically with several electrical phases.
Electrical swivels are commonly used in robotics, in particular on production lines.
They are also used in more specific applications, for example at sea to establish an electrical connection between an underwater device and a ship.
FIG. 1 illustrates such an example of use. As illustrated, an electrical swivel 100 is used here on board a ship 105 to establish an electrical junction between a cable 110 connected to an underwater electrical system (not shown) and a cable 115 connected to an electrical system of the ship 105.
In such an application, referred to as “offshore”, the electrical swivel is generally a high-voltage electrical swivel used for voltages greater than 1 500 V for direct current or 1 000 V for alternating current, enabling the transfer of high electrical power between a fixed structure linked to the sea bed and a mobile part such as an FPSO (initialism of Floating Production, Storage and Offloading vessel).
Electrical swivels used in such applications must meet predetermined quality requirements to provide a certain level of security, in particular in an explosive atmosphere.
For such purposes, the electrical swivels implemented generally comprise an internal chamber within which are placed conducting tracks and associated brush assemblies. The internal chamber is filled with a dielectric fluid, typically oil.
The dielectric fluid enables each conducting track to be insulated in order to prevent electrical arcs forming with neighboring conducting parts (generally metal parts) and to reduce the distance between the conducting tracks. More particularly, the minimum distance between the conducting tracks is linked to the dielectric strength of the medium in which they are located, it being possible for the dielectric strength of oil to be ten times higher than that of air (under standard pressure, for example a normal pressure of one atmosphere). It is to be recalled here that the dielectric strength of a material is expressed in kV/mm (kilovolts per millimeter) and characterizes the maximum electric field that may be applied between two different electrodes before an electric arc is produced and therefore breakdown.
However, although the dielectric strength of oil is much greater than that of the air and enables the distances between the conducting tracks to be significantly reduced, these distances are also linked to the electrical voltage at the terminals of the electrical swivel. Thus, for high voltages, the electrical swivels are necessarily of large size and require a high quantity of oil. This results in devices that are heavy and bulky.
The invention enables at least one of the problems set forth above to be solved.